hazards and uses

• what is radioactive contamination?


  the presence of unwanted radioactive nuclei on other materials
• what is irridation?


  the process of exposing a material to nuclear radiation but the material does NOT become radioactive.
• give 3 applications of radioactive materials

  medical tracers, radiotherapy and smoke alarms
• what kind of radiation is used in smoke alarms?

  alpha radiation
• how do smoke alarms work?

  alpha radiation is emitted into the air, reaching a detector and completing the circuit. if smoke is present, it blocks the alpha radiation so it does not reach the detector, therefore not completing the circuit and causing an alarm to ring.
• give a use of beta emitters

  thickness monitoring of paper.
• how does thickness monitoring work?

  a source and a receiver are placed on either side of the sheet. if there is a drop or a rise in the number of particles detected, the thickness has changed and needs adjusting.
• why are isotopes with long half-lives particularly harmful?

  because of their longer half lives, they remain radioactive for a much longer period of time and therefore need to be contained to avoid humans and the environment from being exposed to radiation for too long.
• state 2 uses of nuclear radiation in medicine.

  examination of internal organs and controlling + destroying unwanted tissue
• how is radiation used in sterilisers?

  gamma emitters are used to kill bacteria/parasites on equipment
• what kind of radiation is used for radiotherapy?

  gamma radiation
• explain the process of chemotherapy

  gamma emitters direct gamma rays ont specific areas with cancerous cells. the cells absorb the radiation and die
• risks of ionising radiation to people

  can damage living cells, causing them to die or mutate and become cancerous
• what is nuclear fusion?

  the joining of two light nuclei to produce a heavier nuclei and release energy
• name 2 isotopes of hydrogen which are commonly used in nuclear fusion.

  deuterium and tritium
• which releases more energy: nuclear fusion of fission?

  nuclear fusion
• explain the difficulty of generating energy through nuclear fusion.

  fusion requires very high temperatures which in itself requires large amounts of energy and also requires casing which can with stand them.
• what can mass be converted into?

  energy
• what is nuclear fission?

  the splitting of large, unstable nuclei to form smaller more stable nuclei (+ the emission of spare neutrons)
• what usually needs to happen to induce fission?

  the unstable nuclei must absorb the neutron. spontaneous fission (no neutron absorption occurs) is very rare.
• alongside 2 smaller nuclei, what else is emitted in a fission reaction?

  two or three neutrons, gamma rays, energy
• what takes place during a chain reaction in a nuclear reactor?

  an unstable nucleus absorbs a neutron, inducing fission and released 2 or 3 more neutrons. this induces more fission and results in a chain reaction.
• ionising radiation and its effects

  LOWER doses = damage living cells by causing mutations in the DNA, which can cause cells to divide uncontrollably causing cancer.

  HIGHER doses = tends to kill cells completely, which causes radiation sickness if a lot of cells get blasted at once
• how dangerous is each type of radiation based on where it is?

  OUTSIDE = gamma and beta are the most dangerous because they have the most penetrating power and can travel further distances, meaning they can pass through skin.

  INSIDE - alpha radiation because it is the most ionising and does all of its damage in a very localised area. gamma will mostly pass through without doing much damage
• irridation and contamination

  irridation depends on the distance from the source and the type of radiation the source emits. contamination is when the radiation is physically touching skin, or has been inhaled / swallowed. however, irridation is when the skin has been exposed to it, so the person is close to it but isn't actually touching the source.
• irridation and contamination

  irridation is temporary if the source is taken away, while contamination is long-term, if the original source is taken away, the atoms causing contamination are left behind, potentially causing more harm.
• hazards depending on its half life

  the LOWER the activity of the radioactivity source is, the safer it is to be around.
• hazards depending on its half life

  if the 2 sources with different half lives contain the SAME number of radioactive nuclei, the one with the longer half life will have have a lower activity [since its atoms are less likely to decay]
• hazards depending on its half life

  if 2 sources with different half lives start with the same ACTIVITY, the activity of the sample with the shorter half life will fall faster than the activity of the one with the longer half life. so after a while, the one with a longer half life will have higher activity = more dangerous
• nuclear fission

  nuclear fission is used to release energy from large and unstable nuclei by splitting into smaller nuclei.

  a nucleus splitting gives out a lot of energy, there is a lot of extra energy which is carried away by gamma radiation
• problems with nuclear fission.

  disposal of waste = the products left over are highly radioactive and have long half lives. they're difficult and expensive to expose of safely.
• nuclear fusion

  releases a lot of energy due to the difference in mass between the original nuclei and the new nucleus. this extra mass is converted into energy.
• benefits of nuclear fusion


  doesn't create radioactive waste
• nuclear fusion only happens at really high temperatues and high pressures. and to keep hydrogen in these conditions, you need an extremely strong magnetic field.
• beta and gamma radiation in smoke alarms

  beta and gamma radiation cannot be used in smoke alarms because of their penetrating power, the smoke would not stop them and they would complete the circuit, not setting off the alarm when smoke is present.